Friction mechanisms of graphite from a single-atomic tip to a large-area flake tip

The frictional mechanisms of graphite derived from a single-atom tip and a graphite flake tip are systematically studied. The frictional forces in both cases are approximately proportional to the loading force because of significant deformation of the graphite surface. For ``atomic friction (single-atom tip),'' the effect of water on the loading force is discussed. The deformation and effective lateral stiffness of the graphite surface under ambient conditions are evaluated using the ``extended Hertz model.'' A single-atom tip attached to the macroscopic tip gives interpretations of atomic resolution of frictional force maps even under high loading conditions. For ``flake friction (flake tip),'' the graphite flake moves on graphite such that the stacking of graphite layers is maintained. In this case, the frictional coefficient along the [1230] direction of the graphite(0001) surface is estimated to be approximately 0.001. The anisotropy of the frictional force as a function of the pulling direction is also shown.